Way to disable "gradient" in ortho views?
Modal Timer Handler, 

Run script, adds a button to info header.  Uses no gradient in ortho mode and gradient in perspective view for all 3d views on screen when ON.  Add a comment if you want changes re side view etc, or setting a default, prob gradient on when OFF.  



wm.event_timer_add(2.0, context.window) makes it tick over every 2 seconds. Change for faster / slower updates.

import bpy
from bpy.props import BoolProperty

class ModalTimerOperator(bpy.types.Operator):
    """Operator which runs its self from a timer"""
    bl_idname = "wm.modal_timer_operator"
    bl_label = "Modal Timer Operator"

    _timer = None

    def modal(self, context, event):
        screen = context.screen
        theme = context.user_preferences.themes[0]

        if not screen.toggle_grad:
            self.cancel(context)
            return {'CANCELLED'}

        if event.type == 'TIMER':
            views = [(a, s) for a in screen.areas 
               if a.type.startswith("VI")
               for s in a.spaces
               if s.type.startswith("VI")]

            for a, s in views:
                theme.view_3d.space.gradients.show_grad = s.region_3d.is_perspective

        return {'PASS_THROUGH'}

    def execute(self, context):
        wm = context.window_manager
        self._timer = wm.event_timer_add(2.0, context.window)
        wm.modal_handler_add(self)
        return {'RUNNING_MODAL'}

    def cancel(self, context):
        wm = context.window_manager
        wm.event_timer_remove(self._timer)

def register():
    bpy.utils.register_class(ModalTimerOperator)

def unregister():
    bpy.utils.unregister_class(ModalTimerOperator)

if __name__ == "__main__":
    register()

def theme_gradient_toggle(screen, context):
    if screen.toggle_grad:
        bpy.ops.wm.modal_timer_operator('INVOKE_DEFAULT')

bpy.types.Screen.toggle_grad = BoolProperty("Auto Gradient", update=theme_gradient_toggle)    
# draw a button in the info header
def draw_button(self, context):
    screen = context.screen
    text = "ON" if screen.toggle_grad else "OFF"
    self.layout.prop(context.screen, "toggle_grad", toggle=True, text=text, icon='RADIOBUT_%s' % text)

bpy.types.INFO_HT_header.prepend(draw_button)
#bpy.types.INFO_HT_header.remove(draw_button)